Step 1: Match Frenkel defect.
Frenkel defect occurs when an ion, generally a smaller cation, leaves its normal lattice position and occupies an interstitial site.
This defect is commonly observed in ionic crystals where there is a large difference in size between cations and anions.
Silver chloride \((AgCl)\) is a common example showing Frenkel defect.
Therefore:
\[
A \rightarrow 3
\]
Step 2: Match Schottky defect.
Schottky defect arises when equal numbers of cations and anions are missing from their lattice sites.
This defect decreases the density of the crystal.
Sodium chloride \((NaCl)\) is a standard example of Schottky defect.
Hence:
\[
B \rightarrow 2
\]
Step 3: Match Vacancy defect.
Vacancy defect occurs when some lattice sites are vacant in a crystal structure.
Thus, crystals with vacant lattice sites represent vacancy defects.
Therefore:
\[
C \rightarrow 4
\]
Step 4: Match Metal deficiency defect.
Metal deficiency defect occurs when metal ions are missing from the crystal lattice, leading to a deficiency of positive ions.
\(FeO\) is a well-known example of metal deficiency defect because some \(Fe^{2+}\) ions are absent from their lattice positions.
Thus:
\[
D \rightarrow 1
\]
Step 5: Write the complete matching.
\[
A-3
\]
\[
B-2
\]
\[
C-4
\]
\[
D-1
\]
This corresponds to option (2).
Step 6: Final conclusion.
Hence, the correct matching is:
\[
\boxed{A-3,\; B-2,\; C-4,\; D-1}
\]
